Stabilization of cracked distillate fuel oils



Jan. 3. 1956 w. H. ALDERSON ET AL 2,729,594

STABILIZATION 0F CRACKED DISTILLATE FUEL OILS Filed Dec. 13, 1952 2 Sheets-Sheet 2 RELATION OF Acm CONCENTRATION AND TREATING TEMPERATURE FOR THE STABILIZATION OF CRACKED FUEL OIL DISTILLATES l H30 150 ACID TREATING TEMP.

I o o o o m 00 h w CIIDV slam-ms JO NOLLVHLNEIONOD INVENTORS WILL/AM H. ALDERSON JOHN H. EASTHAGEN ATTORNEYS poration, San Francisco, Calif., a corporation of Delaware Application December 13, 1952, Serial No. 325,838 Claims. (Cl. 196-38) This invention relates to a process for treating cracked petroleum hydrocarbons and, more particularly, to a process for stabilizing cracked distillate fuel oils useful as fuels for industrial and household furnaces or burners, as fuels for diesel engines, and the like. i i

Thermally or catalytically cracked petroleumhydrocarbons boiling within about the range of 300 F. to 750 F, generally known as cracked distillate fuel oils, such as cracked gas oil, and which find utility as furnace oils, diesel fuels, and the like, sutfer from the disadvantage of instability. During storage, such oils develop objectionable color characteristics and gum-like oil-insoluble materials or sludges which uponuse cause plugging and clogging of filters, screens, and burner tips, thus detracting from their usefulness, and impairing their marketability. Also, in refinery practice, it is often advantageous to form blends of cracked fractions with straight-run stocks for the uses above enumerated. For example, products from catalytic cracking plants include a partly or completely converted stock in the gas oil boiling range, called catalytic cycle oil! A-n advantageous disposition of this cycle oil is its use as furnaceoil blended with straight-run oils, for example, straight-run gas oil. inclusion of the cycle oil in the. furnace oil, however, so impairs the stability of the blend that it is often necessary to divert it to black fuel .oil of lower value. Generally, blends of straight-run and cracked distillate fuel oils are incompatible; that is, the blend is substantially less stable than either of the components before blending. Such blends, because .of their incompatibility, 1. 33 6 not enjoyed wide acceptance. i

We have now found that we can overcome the problem .of instability attendant cracked petroleum distillate fuel oils by a process which entails essentially two steps. Broadly, the process is ;car ried out by subjecting .the cracked distillate, for example, cracked ,gas oil, to a treatment with sulfuric acid followed by an alkali ,or caustic treatment. We have found, moreover, that tlie acid and caustic treatments must be carried (out under critical conditions, such as amounts, .ccncentrations, and temperatures, in order to obtain a final product which does not require rerunning or redistillation or a plurality of treatments tornake it satisfactorily stable. Advantageously, following the caustic treatment, the product is waterwashedand dried.

More specifically, the invention contemplates the stabilization of cracked distillate fuel 'oils and the :preparation of compatible blends of cracked .distillatesj with straight-runroils by a process which comprises contacting the unstable cracked distillate with sulfuric acid at a temperature varyingwiththe concentrationor strength of the acid, thereafter separating an oil phase from an acid phase, contacting the oil phase with an excess of a hot alkali of caustic solution, and thereafter separating an oilphas'e from an alkaline phase. Following the caustic .step, the oil phase is desirably'washed and-dried,'as-with air. *By ,acid strength or concentration we mean the lady. temperature results in a failure to segregate and remove preferably about 60 F. Optimum operatingzconditions 2,729,54 atent J n- 3 ,9 .6

2 fieetive treating strength or concentration of the acid defin by th ra io 2 04. msor+ 20 o a e gh ba is As hereinabove indicated, we have found that there exists a definite relation of acid concentration and treatitig temperature. In general, the temperature in the acid treating stepvaries inversely with the concentration or strength of the acid. At a high treating temperature, an acid or low concentration is employed. Conversely, at a low treating temperature an acid of higher concentration is employed. Moreover, we have found that the use Oftreating temperatures and acid concentrations beyond certain higher limits gives undesirable results. Likewise, the use of treating temperatures or acid concentrations below certain lower limits gives undesirable results. Thus, the use of too high a temperature for a given acid concentration or toohigh a concentration for a given temperature results in the formation of neutral reaction products which on storage .of the oil, especially at elevated temperatures, are converted to undesirable acidic materials. On the other hand, if treating temperatures or acid concentrations a e too low, no substantial improvement in the oil, is noted. In general, as will hereinafter he more fully shown, temperatures can be employed rangir g from about 50 F. to as high as about 220 F. and anacid r ging in concentration from about 60% for the higher temperature to higher than (fuming sulfuric), for the lower temperature limit.

t has been ascer ine t e precipitates nd sum which a cracked distillate fuel .oil, such as cracked gas oil, deposits on aginghave their source in the polar fraction of the oil, and are formed by oxidation of the latter. Thus, stocks from which the polar fraction has been removed, as by adsorption, are stable with respect to color en eum .fc matio ih p ar fraction a n s o b tween about 0.5% and 3% of the whole cracked stock. Qhroniatographic and hemical analyses .of this polar fraction show that it contains material of varying polarity of acidic, basic, phenolic, and neutral nature. While the sum-far i abi tyo the m st p a fractions i g eatest, l'l fractions contain unstable constituents. These polar fractions are con erted to gums on contact with air, and gum formation accelerated at elevated temperatures.

In view of the foregoing explanation of the nature .of the deposits, gums and sludges. formed in the oil during storage, it is believed that the function of the acid in the acid-treating step of the inventive process is to segregate n emo e po ar compounds sh m ca re io o by solubilization orby both. To effect such segregation and removal in a manner to produce satisfactory results, we have found that, as hereinabove indicated, the concentration or strength of the sulfuric acid and the treating temperature are correlative. Thus, if the concentration .of

the acid for a given temperature is too high, deleterious materials are formed in the stock which later on aging yield acidic products and render the oil corrosive. Simian acidjconcentration that is too low for a given thepolarcompounds. In general, itis preferred to operate with an acidlcqncen'tration no higher than about 96% withfla maximum temperature for this concentration of about 98 F, ands low temperature of about 50 F.,

are an acid concentrationof about 33% to about88.% and a temperature between about 80 F. and F, any temperature within this range being suitable for any cont a nw h n th spe i d Qns=e t s ran e "T m t o aqidsaa a w e and t end is a lar-g'e'xtentou the amount and nature of the polar matreated.

. The function of the caustic is to neutralize oil-soluble sulfonic acids and other free acidic materials, to remove entrained sulfuric acid, and to hydrolyze potentially acidic materials and neutralize the acids thus formed. By potentially acidic oil-soluble materials, it is meant to include those materials which are potential acid-forming materials, that is, materials capable of generating acidic materials or breaking down into acidic materials, such as esters, and which are undesirably present in the oil. I

In order to effect the proper degree of neutralization and particularly to effect hydrolysis of potentially acidic materials with subsequent neutralization of acid products, the temperature at which the caustic treating step is carried out has been ascertained to be critical. At a temperature below about 150 F., the rate of hydrolysis of the aforesaid materials is so slow as to render the process impractical. Above a temperature of about 250 F., it has been noted that not only is special and expensive equipment resistant to corrosion required, but that also no particular benefits in the final product are noted. In summary, while a temperature range of about 150 F. to about 250 F. is suitable, a preferred range resides within the temperature limits of about 180 F. to 200 F.

In carrying out the caustic or alkali treating step, sufficient contact time of the oil to be treated with an excess of caustic is provided so that, associated with the feature of an elevated temperature, complete reaction of all acidic products, including the potentially acidic products, with the caustic can be effected. Generally, the time required for the mixture of caustic solution and oil to separate into an oil phase and an alkaline aqueous phase, that is, about 15 to about 45 minutes, has been ascertained to be of suf ficient duration to bring about complete reaction at the elevated temperatures above noted.

Also, in carrying out the caustic or alkali-treating step,

an excess of caustic or alkali over the amount required to effect complete reaction of acidic and potentially acidic materials is employed. The amount of caustic is so regulated that upon separation of the aqueous phase from the -oil phase in the caustic treating step, the aqueous phase is still alkaline, and preferably has a pH of at least 8% -In place of a caustic or alkali solution formed from an of about 10 B. (American standard scale), although solutions of about B. to 20 B. can'be employed, if desired. The use of solutions of density higher than about 20 Be are less desirably employed, since they result in the formation of undesirable oil emulsions and loss of stock through entrainment of oil in the caustic solution. Generally amounts of caustic sodas or molar equivalents of other bases, residing about within the range of 0.2 pound to 0.7 pound, preferably 0.25 to 0.35 pound caustic based on dry caustic per barrel of oil will be found suitable. Further features and advantages of the invention will be apparent from the following description of the invention given in connection with the appended Figures 1 and 2 which illustrate, respectively, a suitable arrangement of apparatus for the carrying out of a preferred embodiment of the invention, and a graph illustrating the relationship of acid concentration and treating temperature.

Referring now to Figure 1, the numeral 1 refers to holdingtank or reservoir for cracked distillate fuel oil, such as cracked gas oil; and the numeral 2, to holding tank or reservoir for sulfuric acid. Oil is withdrawn from holding tank 1 through line 3 and passed through heat exchanger 4, wherein the temperature of the oil is raised with acid-treated oil.

to the desired temperature depending on acid concentration, after which it is introduced through line 6 into mixing zone 7. In mixing zone 7, the oil is intimately admixed with sulfuric acid taken from holding tank 2, the acid being introduced into the mixing zone through line 8, provided with valve 9, and line 6. Mixing zone 7 is provided with any suitable apparatus capable of effecting intimate admixture between acid and oil, such as baffied pipes wherein a high degree of turbulence can be effected.

From mixing zone 7, the mixture of oil and acid is passed through line 11 into acid settler 12. In order to facilitate settling, acid settler 12 is provided with settling aids, such as acid-inert packing and bafiles. In settler 12 the mixture of hydrocarbon oil and acid separates into a top hydrocarbon oil phase and a bottom acid phase. The acid phase is withdrawn through line 14, and part or all of the withdrawn acid may be recycled through line 15 to line 6 for use in further mixing with incoming oil or part or all of the acid may be removed from the system through line 16. The oil phase is withdrawn from settler 12 through line 17 and therein mixed with alkali taken from alkali storage 20 and passed through line 18, provided with valve 19, into line 17. The stream of alkali and oil is then subjected to intimate admixing in mixing zone 21, which may be provided with apparatus similar to that of mixing zone 7. The mixture of oil and alkali is then passed through heat exchanger 22 wherein the temperature of the mixture is raised to between about 150 F. and 250 F., and thereafter introduced through line 24 into alkali settler 25. After a residence time of about 15 to 45 minutes in alkali settler 25, during which reaction of acidic, and potentially acidic materials with the caustic is completed, and the mixture separates into a top hydrocarbon oil phase and a bottom aqueous alkali phase, the aqueous alkali phase is withdrawn through line 26 and through line 27, and recycled to line 17 for further contact After the alkali is spent it is removed from the system through line 28. The caustic treated oil is withdrawn from alkali settler 25 through line 30, contacted with water introduced through line 32,

bottom water phase, the water phase being withdrawn through line 37 and the oil phase, through line 38 and sent to product storage 40. As hereinbefore indicated, the oil after separation from Water may be dried prior -to use.

Referring to Figure 2, the triangle ABC, labeled Area of satisfactory treatment defines the area within which satisfactory ranges of treating temperatures and acid con centrations may be selected for the treatment of cracked fuel oil distillates in accordance with the present invention. Reference to the graph affords ready means for the selection of an appropriate range of treating temperatures for any given acid concentration or a satisfactory range of acid concentrations for any given treating temperature.

Theline BC, labeled Upper limit for control of acidity,

defines the upper limit of acid concentration that can be tolerated for any given temperature. Line AC, on the other hand, labeled Lower limit for sufficient treatment defines the lower limit of acid concentration for a given temperature which can be employed and yet produce satisfactory results.

A convenient method of determining the stability of .a cracked distillate fuel oil, and the one used in obtaining the data hereinbelow appearing, is the so-called .Filter residue test, according to which test the amount of insoluble solids finer than mesh present in distillate fuel oils, in parts per million, by weight, is determined. The test is carried out as follows: A sample of the oil to be tested is first screened through a 100 -mesh sieve into an unstoppered quart bottle to give conturbid-391i tact with air, the bottle then being placed in at own and heated for four weeks 'at a temperature of 140 E, in order to accelerate aging. After aging, the sample is withdrawn from the oven and "allowed to 'cool.

A Gooch crucible is prepared by placing a piece of filter paper atthe bottom of a tared crucible, and a filter mat is formed by pouring a slurryof tasbestos ft hereover. The crucible is then dried in an oven at 190 F. for one to one and one-half hours and stored in a constant humidity vessel for at least three hours before Weighing. The crucible is then weighed and the weight noted (a), the weight of the dried mat also being noted (b).

A weighed 500 .ml. portion ('0) of the cooled sample is transferred to a separatory funnel. "The separatory funnel is mounted over "the G'ooc'h crucible so that the stem of the funnel extends well into thecrucible. The sample is then filtered by suction, and the filtered oil retained undiluted for use in calculating the Adsorption factor. 7

The empty sample bottle is then 'washed thoroughly with filtered petroleum ether, and the washings passed through the separatory funnel and filter. Two additional 25.0 ml. portions of filtered petroleum ether are added to the separatory funnel and filtration is carried out at a reduced suction rate so that the petroleum ether filters slowly. The walls of the crucible, inside and outside, and the tip of .athe vse'paratory funnel are washed with filtered petroleum ether, after which the crucible is sucked dry, placed in man oven at about 190 for one to one and one-half hours and then placed in a constant humidity vessel for at t'least three hours. The weight of the crucible is then determined '(d').

The retained oil from the first filtration is passed through a second Gooch crucible prepared like the first mentioned one, the :crucibleclraving :been atared (a), so that the actual weight of the filter mat is known 6 The Lcrucible is washed with petroleum ether "and dried as in the first-described filtration operation; Therdri'ed crucible is weighed and the weight noted (g). These weights are used in 'calculatin'g'the Adsorptionfactor.

The material adhering to the walls of "the sample bottie is dissolved with a hot mixture of 8'1V0ll11116830f ben- Zene plus 2 volumes of :ethyl alcohol.- The .solvent :gum mixture is .then evaporated to dryness in a small tared beaker, and then weighed (11;).

.Filter residue, in :partsper milliofi of fuel on, by weight, is calculated by means of the following equations: w -=1). p. m. *Eilterrresidue wherein A satisfactory cracked distillate should have a filter residue not exceeding about ZSparts of-unfilterablematter by weight per million parts "fuel by weight.

The method utilized for determining the presence or absence of undesirable acidic products following treatment in accordance with the inventive process, 'isthe =so-called Delayed hydrolysis test." Accordingtothis test,the acid and caustic-treated sampleis water-washed and filtered. It is then placed in "a "stillwhichhas previously i been carefully cleaned by steaming until both overhead and bottoms are free fromcontamination.

The sample is refluxed for 6 hours in the presence of steam. During refluxing "a small amount of steam condensate is bled from theLcondenser'whil'e a small amount of steam is continuously injected into the still. The

sample is then cooled, withdrawnfromthe still and washed with about by volume, of distilled watcrmand the pHof the water after washing and of the condensate are determined. The pH of the wash water and of the condensate for a satisfactorily stable oil should not be below about 5.

The following examples are given :further to illustrate the invention but are not to be construed as limiting the invention thereto.

Example 1 Catalytically cracked gas oilhavingan ASTM D-158 distillation range of 422 F. to.606 -E., a sulfur content of 098% (ASTM, Lamp), and an API gravity of,23..'3 was heated to a temperature of about 5100" and intimately admixed with sulfuric acid in an amount of about 10 pounds of acid per barrel of hydrocarbons. The acid-treated hydrocarbons, after phase separation from the acid, were treated with 10 volume percent of 10 Be. sodium hydroxide at 200 for one-half hour, after which the mixture of sodium hydroxide separated into an aqueous caustic phase and ahydrocarbon phase. The hydrocarbon phase wasseparately washed with water and then dried with air. A filter residue test performed on the hydrocarbon phase gave a value of 2 p. p. m., whereas the original .oil had a'filter residue of 289p. .p. In.

Example 2 A sample of the treated hydrocarbons obtained by -Example l was mixed with an equal volume of a straightrun gas oil having an ASTM D-158 distillation of 354-to 630 F., a sulfur content of 0.35% (ASTM, .Lampj), an API gravity of 38.1", and a filter residue of 0 p. p. m. The filter residue of the blend was 1 p. p. m., whereas the filter residue of a blend prepared from equal volumes of the same straight-run gas oil and untreated cracked distillate described in Example 1 had a filter residue of 275 p. p. m.

A second blend of 25% of thesame treated oil and 75% of the same straight-run oil had a filter residue of 0 p. .p. m.

Example 3 A thermaliy cracked gas oil derived from a-California crude oil having an A'STM D-l5-8 distillation range-of about 470 F. to 625 F, a sulfur content of 1:0% (ASTM, Lamp), and an API gravity of 24 was treated at 70 F. with 5 pounds of spent alkylation acid (96% H2804) per barrel of oil. Following separation of the hydrocarbon phase from the acid phase, the hydrocarbon phase was treated as in Example 1 exceptthatthe caustic treating step employing 10% by volume of 1.0 Brcau stic was carried outat a temperature of only 75 F. After the caustic treating step, the hydrocarbon phase was separated from the aqueous causticphase. This hydrocarbon phase had a filter residue of 121 p. p. mas :compared with p. pm. or" a sample of the .untreat edoil, which illustrates that in order for the caustic treating step to be effective in reducing the filter residue to satisfactory limits higher temperatures must be employed.

A second sample was treatedlin .a ,similarmanner as above, except that 20 poundsof spentalkylation acidper barrel of oil were employed. The .filter residue of .the

tfinished product was still very high, namely 72p. p. m.

Example 4 A catalytically cracked gas oillhaving an ASTM D1158 distillation range of 478 to 610 F., a sulfur contenttof 0.97% (ASTM, Lamp), and an API gravity of 23.9 was divided into four portions. 7 7

One portion was treated in acordan'ce with Exampleil, except that 96% sulfuric acid and a-temperature1of.,1f50' F. were employed in the acid treating step. A-delayed hydrolysis test on the finished sample gave a pH of 3.0, indicating that acid concentration or temperature was too high for satisfactory acidity control.

The second portionof the cracked distillatewas treated as in Example 1, except that 91% .sulfuricacid anda temperature of were employed .in the acid treating .step. ThepH of the water wash, determinedwin accordance' with the delayed hydrolysis test above noted, was still too low at 3.3.

The third portion was similarly treated as the first and .second portions except'that 75% acid and a temperature of 150 F; were employed in the acid-treating step. This sample passed the delayed hydrolysis test by giving a pH of 6.0.

' The fourth sample was treated like all the others except that 85% acid and a temperature of 100 F. were employed in the acid treating step. This sample also passed the delayed hydrolysis test by giving a pH of 6.7.

Example A catalytically cracked gas oil having an ASTM D-158 distillation range of 482 F. to 600 F., a sulfur content of 0.9% (ASTM, Lamp), and an API gravity of 25.6", was divided into two portions. One portion was treated as in Example 1, except that 60% sulfuric acid and a temperature of 200 F. were employed in the acid treating step. The finished oil failed the residue test, giving a value of 30 p. p. m.

The second portion was similarly treated, except that an acid of 75% strength and a temperature of 150 F. were employed in the acid-treating step. The filter residue of "the finished oil was p. p. m. and the delayed hydrolysis cated in the appended claims.

We claim:

1. The process of stabilizing a hydrocarbon cracked petroleum fuel oil distillate boiling within about the range of 300 F. to 750 R, which comprises intimately admixing in a single acid treating stage said cracked petroleum fuel oil distillate at a temperature within about the range of 50 F. to 220 F. with sulfuric acid of a concentration of at least 60% and varying inversely with the temperature within the specified temperature range, isolating an acid phase and an acid-treated hydrocarbon phase, contacting in a single caustic treating stage said acid-treated hydrocarbon phase at a temperature within about the range of 150 F. to 250 F. with an aqueous alkali metal hydroxide solution of 5 B. to B. to

'react with free acidic and potentially acidic materials to yield an alkaline phase and a hydrocarbon phase, isolating said hydrocarbon phase, water washing and drying said hydrocarbon phase to produce the finished product.

2. Process as described in claim 1, wherein the cracked fuel oil distillate is intimately admixed with sulfuric acid at a temperature'between about 80 F. and 110 F. and

the concentration of the sulfuric acid is between about 83% and 88%.

3. Process as described in claim 2, wherein the acidtreated hydrocarbon phase is contacted with the alkali metal hydroxide solution at a temperature between about 180 F. and 200 F.

4. Process as described in claim 3, wherein the alkali metal hydroxide solution is a sodium hydroxide solution .and the amount used is about 0.2 pound to about 0.7 pound based on dry sodium hydroxide per barrel of fuel 5. The process of continuously treating a hydrocarbon cracked petroleum fuel oil distillate boiling within about v the range of 300 F. to 750 F. to stabilize it and to render ,an acid concentration falling within the area ABC of appended Figure 2, isolating an acid phase and an acidtreated hydrocarbon phase, contacting in a single caustic treating stage said acid-treated hydrocarbon phase at s. temperature within about the range of 150 F. to 250 8 F. with a solution of alkali metal hydroxide of about 5 B6. to about 20 R6. for about 15 minutes to about 45 minutes to react with acidic and potentially acidic materials to yield an alkali metal hydroxide phase and a hydrocarbon phase, isolating said hydrocarbon phase, water washing and drying said hydrocarbon phase to produce the finished product.

6. Process as described in claim 5, wherein the acid concentration is not higher than about 96%.

7. Process as described in claim 6, wherein the acidtreated hydrocarbon phase is contacted with the alkali metal hydroxide solution at a temperature of about 180 F. to 200 F.

8. Process as described in claim 6, wherein the alkali metal hydroxide is sodium hydroxide used in an amount of about 0.2 pound to about 0.7 pound, based on dry sodium hydroxide, per barrel of fuel oil.

9. The process of treating a cracked petroleum fuel oil distillate boiling within about the range of 300 F. to 750 F. to stabilize it and render it compatible with a straight-run gas oil boiling within about the same range,

:"which comprises intimately admixing in a single acid treatin'g stage said cracked petroleum fuel oil distillate at a temperature between about F. and F. with about 2 pounds to 20 pounds of sulfuric acid per barrel of fuel ,oil, the acid having a concentration between about 83% and 88%, thereafter isolating an acid phase and an acidtreated petroleum fuel oil phase, contacting in a single caustic treating stage the petroleum fuel oil phase for about 15 to 45 minutes at a temperature between about F.

and 200 F.with a sodium hydroxide solution of 5 B.

to 20 B. and in an amount of about 0.2 to 0.7 pounds of sodium hydroxide, based on dry sodium hydroxide, iso lating a sodiumhydroxide phase and an acidand caustictreated petroleum fuel oil phase, and water washing and drying said petroleum fuel oil phase to produce the finished product.

10. A method of preparing a fuel oil blend of petroleum hydrocarbons boiling within about the range of 300 F.

to 750. F., having a filter residue value not exceeding 25 p. p. m. and containing cracked petroleum hydrocarbons boiling within said range as one component, which comprises treating non-compatible cracked petroleum hydrocarbons boiling within about the range of 300 F. to 750" vF., havinga filter residue value exceeding 25 p. p. m. by

alkali metal hydroxide solution of 5 to 20 B. to produce upon separation-a-hydrocarbon phase substantially free of .acidic constituents and a further quantity of neutral constituents causing incompatibility, separating from the substantially compatible treated cracked hydrocarbons with other hydrocarbons boiling within the range of about 300 F. to about 750 F. to produce a compatible blend having a filter residue not exceeding 25 p. p, m.

References Cited in the file of this patent UNITED STATES PATENTS 1,936,210 Retailliau Nov. 21, 1933 2,025,255 Taylor et a1 Dec. 24, 1935 2,043,936 Story June 9, 1936 2,315,738 Ryan et a1 Apr. 6, 1943 

1. THE PROCESS OF STABILIZING A HYDROCARBON CRACKED PETROLEUM FUEL OIL DISTILLATE BOILING WITHIN ABOUT THE RANGE OF 300* F. TO 750* F., WHICH COMPRISES INTIMATELY ADMIXING IN A SINGLE ACID TREATING SAID CRACKED PETROLEUM FUEL OIL DISTILLATE AT A TEMPERATURE WITHIN ABOUT THE RANGE OF 50* F. TO 200* F. WITH SULFURIC ACID OF A CONCENTRATION OF AT LEAST 60% AND VARYING INVERSELY WITH THE TEMPERATURE WITHIN THE SPECIFIED TEMPERATURE RANGE, ISOLATING AN ACID PHASE AND AN ACID-TREATED HYDROCARBON PHASE, CONTACTING IN A SINGLE CAUSTIC TREATING STAGE SAID ACID-TREATED HYDROCARBON PHASE AT A TEMPERATURE WITHIN ABOUT THE RANGE OF 150* F. TO 250* F. WITH AN AQUEOUS ALKALI METAL HYDROXIDE SOLUTION OF 5* BE. TO 20* BE. TO REACT WITH FREE ACIDIC AND POTENTIALLY ACIDIC MATERIALS TO YIELD AN ALKALINE PHASE AND A HYDROCARBON PHASE, ISOLATING SAID HYDROCARBON PHASE, WATER WASHING AND DRYING SAID HYDROCARBON PHASE TO PRODUCE THE FINISHED PRODUCT.
 2. PROCESS AS DESCRIBED IN CLAIM 1, WHEREIN THE CRACKED FUEL OIL DISTILLATE IS INTIMATELY ADMIXED WITH SULFURIC ACID AT A TEMPERATURE BETWEEN ABOUT 80* F. AND 110* F. AND THE CONCENTRATION OF THE SULFURIC ACID IS BETWEEN ABOUT 83% TO 88%. 